1. Field of the Invention
This invention relates to a robot arm coupling apparatus, and more particularly, to a coupling apparatus for quickly connecting and disconnecting a tool or the like to and from a robot arm.
Generally, a coupling apparatus having an inner assembly attached to a robot arm, an outer assembly to which a tool or the like is attached and locking means which locks the outer assembly to the inner assembly has been known as a coupling apparatus for connecting and disconnecting a tool or the like to and from a robot arm. For example, U.S. Pat. No. 4,696,524 discloses such coupling apparatus having locking means comprising a piston member supported by the inner assembly slidably between the locking position and the unlocking position, a plurality of ball member surrounding said piston member and supported by the inner assembly and a ball retainer supported by the outer assembly and contractable with said ball member of the outer assembly at the tapered surface which, when the piston member moves to the locking position, connects and supports both assemblies in cooperation with the ball member. According to this apparatus, when the piston member moves to the locking position, the ball member pushes upwardly the outer assembly through the medium of the tapered surface, whereby the inner assembly and the outer assembly are locked to each other.
In the above coupling apparatus, however, when the piston member is in the locking position, a cylindrical surface extending in parallel with a sliding direction of the piston member makes contact with the ball member and therefore if there are processing irregularities for the inner assembly, the outer assembly, etc., the ball member cannot be moved exactly to the locking position. Thus, in locking the inner assembly and the outer assembly to each other, there is a fear that the contact surfaces of both assemblies do not mate exactly with each other.